Pulverizers of the above-mentioned type are used in particular in laboratories in order to pulverize samples, which are subsequently subjected to a chemical analysis. It has thereby been proven to be necessary to proceed particularly carefully during a pulverizing of the respective substances since the preparation of the sample substance decisively influences the results of the analysis. When using the most modern analysis methods, it is possible to significantly reduce the amount of the necessary material. This results in shorter sample preparation times and in a considerable savings of material. In the case of very small sample volumes, the demands on the crushing task, namely the pulverizing of the samples, increases considerably since the substances to be analyzed must be separated very finely and this has proven to be disadvantageous. The necessary grain sizes are thereby in most cases less than 0.1 mm. Since furthermore the substances to be pulverized are usually predried, a considerable dust formation occurs caused by the fine pulverization and by the predrying of the substances.
This dust formation demands, in particular in the case of health-hazardous substances, that the operators wear breathing or dust masks, which always prove to be uncomfortable and very hampering. It is furthermore necessary to thoroughly ventilate the respective work space in order to prevent it from becoming dirty because a dirty pulverizing space can result in adulteration of pulverized samples.
For environmental reasons, it is not possible to blow the pulverization dust into the surrounding environment. The system of taking dust out of a work space always requires many apparatus and is therefore very expensive. In addition, these apparatus operate with a high level of noise, also the danger of sample losses exists.
The basic purpose of the invention is to provide a pulverizer of the above-mentioned type, which minimizes the nascent amount of dust, has a simple design and is safe and easy to operate.
The purpose is inventively attained by arranging the pulverizer in a housing having at least one air-inlet opening and one air outlet, by the air outlet being arranged on the bottom side on the housing and being connected to a vacuum source and by providing a filter in the area of the air outlet, which filter can be connected to an air source loading the filter with compressed air in counter-flow direction.
The inventive pulverizer has a number of significant advantages. The arrangement in the housing makes it possible to catch the dust, exiting between the individual structural parts of the pulverizer due to leaks, in a safer method. Furthermore, it is possible to open the pulverizer inside of the housing, for example, to clean the pulverizing device. By connecting the air outlet to a vacuum source, it is assured that a sufficient air flow through the housing exists at all times guiding the dust particles in a safe manner to the filter of the air outlet where these at least partially are caught and are filtered out. The filter in the area of the air outlet is provided in order to prevent an excessive dust load on the vacuum source. The possibility of connecting the filter to an air source loading the filter with compressed air in counter-flow direction facilitates a regeneration of the filter, with the dust particles accumulated on the filter dropping back onto the bottom of the housing, accumulating there and at some time being removed manually with a shovel or by means of a vacuum cleaner.
Thus the inventive pulverizer assures that dust cannot exit into the work space during the pulverizing operation. Thus, it is possible to use the pulverizer in the usual laboratory spaces, whereas in the case of the state of the art, it was necessary to operate the pulverizer, because of the strong dust formation, in a separate room.
The inventive regeneration of the filter by means of counter-flowing compressed air must be carried out no earlier than after five, in most cases only after 10 or more pulverizing operations. It guarantees a uniformly high intensity of vacuuming the dust from the housing and enhances the life of the vacuum source, since the there existing dust collector is not directly observable. The dust collector already becomes through this ineffective, according to experience, after a short period of operation due to it being overfilled, which leads to a loss of the vacuum source and thus the vacuuming task.
Since air flows always through the housing of the inventive pulverizer, the danger of a dust explosion is avoided. It is furthermore possible to effectively dampen the noise development coming from the pulverizer through the housing. Furthermore, the occurring material loss is reduced to a minimum, since during the subsequent removal of the collecting reservoir an air flow for the purpose of ventilation does not need to exist in the work space.
The inventive pulverizer is constructed preferably so that the dust-filled air in the housing is exchanged at least one time per second with fresh air.
An advantageous further development of the inventive pulverizer exists by the vacuum source being constructed in the form of a vacuum mechanism provided with a dust collector. The vacuum mechanism can thereby be designed in the form of a commercially available vacuum cleaner. Since a separate, regenerable filter is provided in the area of the air outlet on the housing, it is assured that only a small amount of dust moves into the vacuum mechanism so that its dust collector need be cleaned at longer time intervals, for example once a year.
The air-inlet opening for producing an air flow directed toward the bottom of the housing is preferably arranged in the upper area of the housing. This development assures that the dust particles are fed to the bottom area and are deposited partly already directly on the bottom without reaching the filter of the air outlet.
To clean the inside of the housing, same is provided advantageously with a closeable, slot-shaped opening for introducing a compressed-air lance. It is possible by means of the compressed-air lance to blow off the pulverizing device of the pulverizer after the pulverizing device was opened and also the inner walls of the housing and to clean off adhering dust and residues of crushed material. The vacuum source sucks in the material loosened during this cleaning and feeds it to the filter of the air outlet. The compressed-air lance can thereby be constructed advantageously such that it, in connection with a suitable arrangement of the opening of the housing, is not possible to guide the compressed-air lance into the pulverizing device of the pulverizer. It is thus avoided that after turning off the motor of the pulverizer the rotor which continues to run yet for a longer period of time can be touched by the lance. Thus it cannot be damaged and the operators are not endangered. The possibility to be able to start already with the cleaning task during a still running rotor does not only considerably shorten the operation, but also increases the cleaning effect.
A particularly advantageous development of the inventive pulverizer exists in the housing, including devices for opening of the pulverizer and for removing the collecting reservoir, which devices can be operated from outside of the housing. This development significantly accelerates the cleaning operation of the pulverizer, since it is not necessary to first wait for a complete vacuuming off of the dust on the inside and for the standstill of the pulverizing device.
For opening of the pulverizing device, the inlet chute together with a lid portion is in known pulverizers usually swung out. In order to prevent dust from exiting from the opening associated with the inlet chute and in order to prevent more air from being able to flow into the housing than is sucked off by the vacuum source, the opening is at least partly covered by means of a perforated plate. The perforated plate is constructed such that only a specific amount of air can be sucked into the housing.
A further advantageous development of the pulverizer exists by the collecting reservoir being open through a filter to the inside of the housing.
This filter has the effect that the low vacuum on the inside of the housing continues into the collecting reservoir. The air flow balancing the vacuum enters the pulverizer at the inlet chute and moves through the inside of the pulverizer--carrying with it the here created pulverization dust--into the collecting reservoir. The narrow filter pores hardly permit crushed material to pass. Thus an accumulation of dust inside of the pulverizer, which accumulation could in the case of a very dusty pulverization (for example of earth) result in a loss of dust through the inlet chute into the surrounding environment, is avoided.
It furthermore has proven to be advantageous to arrange the motor outside of the housing. A sufficient cooling of the motor is in this manner assured, on the other hand its contamination with pulverization dust is prevented.
Furthermore it has proven to be advantageous that the housing has air-inlet openings in the area of its corners and edges. Since a defined air flow can always enter through the air-inlet openings, it is prevented that larger amounts of dust settle in the corners or edges.
A cleaning of the filter of the air outlet is done preferably by means of a water-jet pipe arranged movably on the housing in an outlet chamber. The water-jet pipe can be loaded with pressure. Since the water-jet pipe is movable, it is possible to load the filter selectively with air in order to remove dust particles adhering over its entire cross-sectional surface.